Sustainability Attitude–Behaviour Score Differences in Two Independent Student Cohorts: Evidence from Higher Education

Universities are expected to play a central role in promoting sustainable development through teaching, research, campus operations and third mission initiatives. Using two independent student cohorts, we examine the relationship between sustainability attitudes and self-reported behaviours among students at a regional public university in southern Greece. Data were collected through two independent cross-sectional surveys conducted in 2022 (n = 409) and 2025 (n = 168), yielding a total sample of 577 students. The questionnaire included 45 items regarding sustainability knowledge, attitudes, and self-reported behaviours, covering environmental, social, and economic dimensions of sustainability, as well as awareness of the university’s environmental strategy. Data were analysed using descriptive statistics, comparative analyses, gap assessment, and cluster analysis. Students reported significantly stronger sustainability attitudes than sustainability behaviours in both cohorts. The mean discrepancy index was 0.426 in 2022 and 0.391 in 2025, and its magnitude did not differ significantly between the two cohorts (p = 0.574, r = 0.023). The analyses did not detect statistically significant differences in overall sustainability attitude scores or self-reported behaviour scores between the two survey cohorts. Given the achieved sample sizes, the study had 80% power to detect standardised cohort differences of approximately d = 0.26 or larger; smaller differences could not be excluded. In the pooled sample, two-step cluster analysis identified higher- and lower-engagement sustainability profiles, with good cluster quality (silhouette measure = 0.60). Participation in student organisations and collective activities was also associated with higher self-reported behaviour after adjustment for available demographic characteristics. The results show that the magnitude of the composite-score discrepancy did not differ significantly between the two cohorts. The findings support further research on whether participatory and context-sensitive university initiatives can complement awareness-oriented approaches. As the results are based on voluntary convenience samples and self-reported measures from one institution, they should be interpreted with appropriate caution.